For dinosaur bones to be found on Mars that would mean that for billions of years Mars would need an atmosphere similar to earth. That atmosphere would be needed to provide water and oxygen to the planet for animals to live. Then for reasons unknown, Mars would then lose that atmosphere.

Maybe a couple bone fragments could have been hurled off Earth during the Chicxulub impact and floated through space before landing on Mars. We have considered that a few meteorites here on Earth have arrived from Mars, so why not the other way around?